Compound screw jack



Dec. 9, 1924. 1,518,490

R. M. DIXON COMPOUND S CREW JACK Filed March 20, 192,@

/NVENTR BY Q Patentedl Dec. 9, 1924.

luNrri-:D STATES PATENT thai RANDALL M. DIXON, OIF STOCKTON, CALIFORNIA.

coMroUNn SCREW Jack.

Application led March 20, 1924. Serial No. 700,516.

part f this application.

This invention relates to improvements in lifting jacks, my main objectbeing to provide a jack of the above named general char-v acter soconstructed that a very powerful raising eect will be had, and loads maybe lifted vthrough 'a considerable distance, while v at the same timethe jack when its parts are fully contracted, will occupy `butrelatively little vertical space.

While my jack may of course be used for any purpose for whichsuch animplement is suitable, I have particularly designed it for automobileservice.

Automobiles must frequently be jacked up, usually to raise an axle sothat a tire may be removed and replaced following a ypuncture orblowout.

In such` cases, and especially when the wheels are equipped withvtheoversize or balloon tires now coming into vogue, the axle will belowered a considerable distance when such a tire loses its air andbecomes flat.' Under such conditions, very frequently the ordinary smalljacks if short enough when contracted to fit between the ground andaxle, have not the liftingvrange necessary to raise the axle therequired'distance,

'or if they have such lifting range, they are too tall evenwhen fullytelescoped or contracted, to ,fit under the axle when the tire is flat.n

The result is that the operator must resort to various time-taking andlaborious expedients in order to be able to jack uphis car. e

M improved jack eliminates the above trou les, by having asbeforestated, a great'.

range of lift coupled with an extremely compact or short size whencontracted.

A further object of the invention is to produce a sim le and inexpensivedevice and yet one whlch willbe exceedin ly effectivefor the purpose forwhich it is designed.

These objects I accomplishiby means of 21 proj ectin such structure andrelative arrangement of parts as will fully appear by a perusal of the'following specification and claims.

In the drawings similar\ characters of reference indicate correspondingparts in the several views: f*

Fig. 1 is a vertical section of the jack with the lifting members partlyraised.

Fig. 2 is an exterior elevation of the jack `in its fully contractedform.

Fig. 3 is a cross section on the` line 3 3 of Fig. 1.

Referring now more particularly to the characters of reference markedthereon, the numeral l denotes a vertical cylindrical casing orpedestal, mounted in the lower end of which is a base pad 2. Turnablymounted on said pad is a bevel gear 3 meshing with a pinion 4whose'shaft or spindle 5 is journaled in a bearing boss 6 formed withthecasing 1. The shaft 5 slopes up at a certain angle, and is bored witha square hole as at 7 or in an manner to non-turnably receive a pin ontelower end of a ratchet turning handle or lever of any suitable form.The outer end of the member 5 is preferably provided with a knurledcollar 8, whereby the pinion may be turned by hand if desired.

The gear 3 has a hollow shaft9 mounted therewith and projecting upwardlyinto the casing for a certain distance and concentric therewith.

This shaft has longitudinal splines 10 on its outer periphery whichengage and slide in splineways- 11 4cut in the bore of a tubular sleeve12. This sleeve is exteriorly threaded throughout" its length with lefthand and preferabl square threads 13 of 'a certain pitch, whic engagewith cooperating threads 14 cut in the bore of the casing for a certaindistance downwardly from the upper end thereof.

In the upper end of the bore of the sleeve 12 are cut rlght hand threads15, also preferably square, which cooperate with similar threads 16 cut'for the full length of astem 17, the bore of the gear-shaft 9 being ofa size tp freely receive said stem therein.

On the upper end of the stem is a fixed pad 18 of suitable size anddesign. Another pad 19 is adapted to rest on the pad 18, being hinged asat 2O to a transverse member j radially under and beyond the pad 18. nthis manner, the upper pad 19 may be swung down out of the way if itsuse isnot deslredhthus enabling the dis# los lll@

. itially setting thejack up to be used. t

22 depending downwardly therefrom and The member 21 projects beyond thepad 18 on the side thereof opposite the hinge 2O and has secured theretoa vertical stem slidable in a sleeve 23 guided by a horizontal boss 24projecting from the upper end of the casing 1. The members 22 and 23have outwardly and inwardly projecting shoulder dportions 25 at theirlower and upper en s respectively, so that when the stem 22 has beenraised a certain distance, its shoulder will engage the shoulder on thesleeve 23 and the latter will then, and not until then, be raised also.The purpose of this telescoping lstructure is to prevent `rotation ofthe jack stem 17.

In operation, if the pinion 4 is turned to the right, the gear 3 andmember 12 will be turned in a clockwise direction. The member 12 beingthreaded into the casing with left hand threads, such rotation willcause the member 12 to be advanced from the casing. At the same time,the 'stem 17 being screwed into the sleeve 12 with threads oppositelycut to those on the outside of the sleeve, and being held againstrotation, is likewise advanced from the sleeve 12 with the advancementofthe latter from the casing. The different screw threads should be ofsuch relative itchthat the lowerl end of the sleeve 12 reac es the lowerend of the cooperatin threads in the casing at the same Vtime as t elower end of the stem 17 reaches the lower end of the cooperatingthreading in the sleeve.

The distance that these members ma travel in the res ective members inWhic they are mounte being substantially equal, both the stem and sleeveshould therefore advance the same distance for each revolution of thesleeve.

It willtherefore be seen that by reason of the telescopin members, theheig t to which the pad may be raised from the top of the casing isconsiderably greater than the total height of the casin itself. l

While le threads on the sleeve are specilied as left hand and thoseonthe stem 17 as ri ht hand, this is only because the pinion 4 1spresumed to be turned to the right to raise-the stem. If the pinion wasintended to be turned in the opposite direction, or the gear was arraned so as to turn counter# clockwise with t e turning of the pinion tofeature of the raisingA the right, then the relative arrangement of 00the threads on the sleeve and ,stem would be reversed.

From'the foregoing description it will be readily seen that I haveroduced such a device as substantially ful) the invention, asv set forthherein.

While this specification sets forth in detail the present and preferredconstruction of the device, still in practice such deviations from suchdetail may be resorted to as do not form a departure from thespirit ofthe invention, as defined by the appended claims. v

Having thus described my invention what- I claim as new and useful anddesire to sef cure by Letters llEatentis:

fills the objects ofA stem normally telescoped therein and capable ofbeing projected therefrom,.a' rod fixed' to and extending parallel withthe stem to move vertically therewith, a sleeve slidably mounted on thecasing and arranged to remain stationary during the initial movement ofthe rod, and means whereby when the rod has moved a predetermineddistance the sleeve will then be raised with any further movement ofsuch rod.

2. A jack comprising a casing, a lifting stem normally telescoped theremand caipable of being projected therefrom, a rod Xed to and extendingparallel with the stem to movevertically therewith, a sleeve slidablymounted on -the casing and arranged to remain stationary durlng theinitial movement of the rod, the rod and sleeve having co-en agingshoulders on their upper and lower en s respectively whereby to causethem to move as a kunit after the rod has moved a predetermineddistance.

3. The combination in a jack of the type described, havin a casing and ajack stem movable vertical y therethrough, of a guide means, such meansincluding a sleeve mounted for vertical slidin `movement relative to thecasin the bore .o the sleeve adjacent its f RANDALL M. DIXON.

of a diameter equal to that of the

